U.S. patent application number 13/602944 was filed with the patent office on 2013-06-06 for image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. The applicant listed for this patent is Hiroki Kawai, Oki Kitagawa, Akiyoshi Shinagawa, Shigeaki Takada. Invention is credited to Hiroki Kawai, Oki Kitagawa, Akiyoshi Shinagawa, Shigeaki Takada.
Application Number | 20130142532 13/602944 |
Document ID | / |
Family ID | 46845638 |
Filed Date | 2013-06-06 |
United States Patent
Application |
20130142532 |
Kind Code |
A1 |
Kitagawa; Oki ; et
al. |
June 6, 2013 |
IMAGE FORMING APPARATUS
Abstract
An image forming apparatus is configured to be able to switch a
target temperature of an image heating member from a standby target
temperature during a standby state in which a pressurizing member
is separated from the image heating member to a first target
temperature or a second target temperature which is lower than the
standby and first target temperatures. The image forming apparatus
controls a contacting/separating mechanism such that a time from
when an image forming signal is input until when the pressurizing
member in the standby state contacts the image heating member and
forms a nip is shorter in a case when the target temperature of the
image heating member is the second target temperature than in a
case when the target temperature of the image heating member is the
first target temperature.
Inventors: |
Kitagawa; Oki; (Kashiwa-shi,
JP) ; Takada; Shigeaki; (Abiko-shi, JP) ;
Shinagawa; Akiyoshi; (Kashiwa-shi, JP) ; Kawai;
Hiroki; (Toride-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kitagawa; Oki
Takada; Shigeaki
Shinagawa; Akiyoshi
Kawai; Hiroki |
Kashiwa-shi
Abiko-shi
Kashiwa-shi
Toride-shi |
|
JP
JP
JP
JP |
|
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
46845638 |
Appl. No.: |
13/602944 |
Filed: |
September 4, 2012 |
Current U.S.
Class: |
399/67 ; 399/122;
399/328; 399/70 |
Current CPC
Class: |
G03G 15/5029 20130101;
G03G 2215/00742 20130101; G03G 15/205 20130101; G03G 15/2032
20130101 |
Class at
Publication: |
399/67 ; 399/70;
399/122; 399/328 |
International
Class: |
G03G 15/20 20060101
G03G015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 2011 |
JP |
2011-264057 |
Claims
1. An image forming apparatus, comprising: an image heating member
configured to heat an image formed on a recording medium; a heater
configured to heat the image heating member; a pressurizing member
configured to pressurize the image heating member to form a nip for
nipping and conveying the recording medium; a contacting/separating
mechanism configured to contact the pressurizing member with the
image heating member and to separate the pressurizing member from
the image heating member; and a control unit configured to control
the heater such that a temperature of the image heating member is
set at a target temperature and being able to switch, on starting
to heat the image formed on the recording medium, the target
temperature at least from a standby target temperature which is the
target temperature during a standby state in which the pressurizing
member is separated from the image heating member to a first target
temperature which is the target temperature in heating an image
formed on a first recording medium or to a second target
temperature which is the target temperature in heating an image
formed on a second recording medium whose basis weight is smaller
than a basis weight of the first recording medium and which is
lower than the standby target temperature and the first target
temperature, the control unit controlling the contacting/separating
mechanism such that a time from when an image forming signal is
input until when the pressurizing member in the standby state
contacts the image heating member and forms the nip is shorter in a
case when the target temperature of the image heating member is the
second target temperature than in a case when the target
temperature of the image heating member is the first target
temperature.
2. The image forming apparatus according to claim 1, wherein the
control unit controls a recording medium feeding time such that a
time from when the pressurizing member contacts the image heating
member and forms the nip until when the recording medium arrives at
the nip is longer in the case when the target temperature of the
image heating member is the second target temperature than in the
case when the target temperature is the first target
temperature.
3. The image forming apparatus according to claim 2, wherein the
control unit controls the recording medium feeding time and the
contacting/separating mechanism in the case when the target
temperature of the image heating member is the second target
temperature such that the time from when the image forming signal
is input until when the pressurizing member in the standby state
contacts the image heating member and forms the nip is shorter than
the time from when the pressurizing member contacts the image
heating member and forms the nip until when the recording medium
arrives at the nip.
4. The image forming apparatus according to claim 2, wherein the
control unit controls the recording medium feeding time and the
contacting/separating mechanism such that the time from when the
image forming signal is input until when the pressurizing member in
the standby state contacts the image heating member and forms the
nip is longer than the time from when the pressurizing member
contacts the image heating member and forms the nip until when the
recording medium arrives at the nip in the case when the target
temperature of the image heating member is the first target
temperature.
5. The image forming apparatus according to claim 1, wherein the
control unit controls the contacting/separating mechanism in
response to the input of the image forming signal such that the
pressurizing member starts to contact the image heating member
after switching the target temperature of the image heating
member.
6. The image forming apparatus according to claim 1, wherein the
standby target temperature is a temperature less than the first
target temperature.
7. The image forming apparatus according to claim 1, further
comprising a thermometer configured to detect the temperature of
the image heating member; wherein when the target temperature of
the image heating member is the second target temperature, the
control unit controls recording medium feeding timing to start to
convey the recording medium when the thermometer detects that the
temperature of the image heating member reaches a predetermined
temperature in a process in which the temperature of the
thermometer drops from the standby target temperature to the second
target temperature.
8. The image forming apparatus according to claim 7, further
comprising a humidity sensor configured to detect humidity within
the image forming apparatus; wherein the control unit sets the
predetermined temperature to be low as the absolute humidity
increases.
9. The image forming apparatus according to claim 1, further
comprising a pressurizing member heater configured to heat the
pressurizing member; wherein the control unit sets a standby target
temperature of the pressurizing member to be lower than the standby
target temperature of the image heating member.
10. An image forming apparatus, comprising: an image heating member
configured to heat an image formed on a recording medium; a
pressurizing member configured to pressurize the image heating
member to form a nip for nipping and conveying the recording
medium; a contacting/separating mechanism configured to contact the
pressurizing member with the image heating member and to separate
the pressurizing member from the image heating member; and a
control unit configured to control power such that a temperature of
the image heating member reaches a target temperature set in
advance; wherein the control unit discriminates a type of the
recording medium, wherein the control unit is able to execute a
first mode of heating an image formed on a first recording medium
by controlling power such that the target temperature reaches a
first target temperature and a second mode of heating an image
formed on a second recording medium having less basis weight than a
basis weight of the first recording medium by controlling power
such that the target temperature reaches a second target
temperature which is lower than the first target temperature,
wherein the control unit is able to execute a standby mode of
standing by an input of an image forming signal by controlling
power such that the temperature of the image heating member reaches
a target temperature higher than the second target temperature in a
state in which the pressurizing member is separated from the image
heating member, and wherein the control unit controls such that a
time from the input of the image forming signal to a contact of the
pressurizing member with the image heating member in the second
mode is shorter than a time from the input of the image forming
signal to the contact of the pressurizing member with the image
heating member in the first mode.
11. The image forming apparatus according to claim 10, wherein the
control unit controls such that a time from the contact of the
pressurizing member with the image heating member to the arrival of
the recording medium to the nip in the second mode is longer than a
time from the contact of the pressurizing member with the image
heating member to the arrival of the recording medium to the nip in
the first mode.
12. The image forming apparatus according to claim 11, wherein the
control unit controls such that, in the second mode, the time from
the input of the image forming signal to the contact of the
pressurizing member with the image heating member is shorter than
the time from the contact of the pressurizing member with the image
heating member to the arrival of the recording medium to the
nip.
13. The image forming apparatus according to claim 11, wherein the
control unit controls such that, in the first mode, the time from
the input of the image forming signal to the contact of the
pressurizing member with the image heating member is longer than
the time from the contact of the pressurizing member with the image
heating member to the arrival of the recording medium to the
nip.
14. An image forming apparatus, comprising: an image heating member
configured to heat an image formed on a recording medium; a
pressurizing member configured to pressurize the image heating
member to form a nip for nipping and conveying the recording
medium; a contacting/separating mechanism configured to contact the
pressurizing member with the image heating member and to separate
the pressurizing member from the image heating member; and a
control unit configured to control power such that a temperature of
the image heating member reaches a target temperature set in
advance; wherein the control unit discriminates a type of the
recording medium, wherein the control unit is able to execute a
first mode of heating an image formed on a first recording medium
by controlling power such that the target temperature reaches a
first target temperature and a second mode of heating an image
formed on a second recording medium having less basis weight than a
basis weight of the first recording medium by controlling power
such that the target temperature reaches a second target
temperature which is lower than the first target temperature,
wherein the control unit is able to execute a standby mode of
standing by an input of an image forming signal by controlling
power such that the temperature of the image heating member reaches
a target temperature higher than the second target temperature in a
state in which the pressurizing member is separated from the image
heating member, and wherein the control unit controls such that a
time from the contact of the pressurizing member with the image
heating member to the arrival of the recording medium to the nip in
the second mode is longer than a time from the contact of the
pressurizing member with the image heating member to the arrival of
the recording medium to the nip in the first mode.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image forming apparatus
including an image heating member configured to heat an image
formed on a recording medium.
[0003] 2. Description of the Related Art
[0004] Hitherto, there is widely used an image forming apparatus
configured to transfer a toner image formed on an image carrier,
i.e., an intermediate transfer member or a photosensitive member,
on a recording medium and to fix the image on the recording medium
by heating and pressurizing the recording medium by a heating nip
composed of an image heating member and a pressurizing member.
Then, lately, the image forming apparatus is required to
accommodate to various types of recording media such as a thick
sheet, a thin sheet and a coated sheet, in addition to a
conventional plain sheet, and it is required to be able to set
different heating target temperatures corresponding to the types of
the recording media for the image heating member that contacts an
image surface in a fixing apparatus.
[0005] Due to that, the image heating member of the fixing
apparatus that is adapted to change the heating target temperature
corresponding to the type of the recording medium is configured to
stand by in a condition of being heated up to a target temperature
of a standby state adjusted for the plain sheet that is frequently
used. When it is commanded here to form an image on a thin sheet, a
temperature adjusting circuit switches the target temperature for
the plain sheet to a target temperature for a thin sheet, which is
lower than the target temperature for the plain sheet. Then, the
image forming apparatus starts to form the image after when the
temperature of the image heating member measured by a temperature
sensor is lowered and stabilized to the target temperature for a
thin sheet.
[0006] In this case, however, it is unable to form the image until
when the temperature of the image heating member converges to the
target temperature for a thin sheet, so that the image forming
apparatus requires a downtime which drops a productivity of the
image forming apparatus. The image heating member is configured to
have a large thermal capacity to reduce temperature fluctuation
during passage of a recording medium in a highly productive image
forming apparatus in particular, so that there is a case when such
apparatus requires a cooling downtime of 10 seconds or more to
lower the temperature just around 10.degree. C.
[0007] In order for that, Japanese Patent Application No.
2000-181274 discloses a fixing apparatus provided with a blower fan
to cool a fusing roller by air. Still further, Japanese Patent
Application No. 2010-139817 discloses a fixing apparatus provided
with a contactable cooling roller to remove heat from a fixing belt
by contacting the cooling roller.
[0008] However, the fixing apparatus is enlarged if the fixing
apparatus is provided with the blower fan or the contactable
cooling roller as described above, in contrary to downsizing of the
image forming apparatus. Still further, an increase of a number of
parts and additional assembly costs pose a problem because they
often turn out be an excessive investment for a thin sheet which is
less used. Furthermore, even when the fixing apparatus is provided
with the blower fan or the cooling roller as described above, it is
required to be able to converge the temperature of the image
heating member more efficiently to the second target temperature
because the cooling downtime is desirable to be as short as
possible.
SUMMARY OF THE INVENTION
[0009] The present invention provides an image forming apparatus
that is capable of reducing a waiting time in forming an image by
quickly lowering temperature of an image heating member. According
to an aspect of the present invention, an image forming apparatus
includes an image heating member configured to heat an image formed
on a recording medium, a heater configured to heat the image
heating member, a pressurizing member configured to pressurize the
image heating member to form a nip for nipping and conveying the
recording medium, a contacting/separating mechanism configured to
contact the pressurizing member with the image heating member and
to separate the pressurizing member from the image heating member,
and a control unit configured to control the heater such that a
temperature of the image heating member is set at a target
temperature and being able to switch, on starting to heat the image
formed on the recording medium, the target temperature at least
from a standby target temperature which is the target temperature
during a standby state in which the pressurizing member is
separated from the image heating member to a first target
temperature which is the target temperature in heating an image
formed on a first recording medium or to a second target
temperature which is the target temperature in heating an image
formed on a second recording medium whose basis weight is smaller
than a basis weight of the first recording medium and which is
lower than the standby target temperature and the first target
temperature, the control unit controlling the contacting/separating
mechanism such that a time from when an image forming signal is
input until when the pressurizing member in the standby state
contacts the image heating member and forms the nip is shorter in a
case when the target temperature of the image heating member is the
second target temperature than in a case when the target
temperature of the image heating member is the first target
temperature.
[0010] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings. The accompanying drawings,
which are incorporated in and constitute a part of the
specification, illustrate exemplary embodiments, features, and
aspects of the invention and, together with the description, serve
to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram explaining a configuration of an image
forming apparatus according to a first embodiment.
[0012] FIG. 2 is a block diagram of a control system of the image
forming apparatus of the first embodiment.
[0013] FIG. 3 is a diagram explaining a configuration of the fixing
apparatus of the first embodiment in section vertical to axes
thereof.
[0014] FIG. 4 is a fixation control flowchart of the fixing
apparatus of the first embodiment;
[0015] FIG. 5 is a time chart of the fixation control implemented
on a plain sheet.
[0016] FIG. 6 is a time chart of the fixation control implemented
on a thin sheet.
[0017] FIG. 7 is a time chart of the fixation control implemented
on a thick sheet.
[0018] FIG. 8 is a fixation control flowchart of the fixing
apparatus according to a second embodiment.
[0019] FIG. 9 is a fixation control flowchart of the fixing
apparatus according to a third embodiment.
[0020] FIG. 10 is a time chart of the fixation control implemented
on a thin sheet according to the third embodiment.
[0021] FIG. 11 is a time chart illustrating effects of the control
of the third embodiment.
[0022] FIG. 12 is a fixation control flowchart of the fixing
apparatus according to a fourth embodiment.
DESCRIPTION OF THE EMBODIMENTS
[0023] Embodiments of the present invention will be explained below
with reference to the drawings.
First Embodiment
<Image Forming Apparatus>
[0024] FIG. 1 is a diagram explaining a configuration of an image
forming apparatus 100 of a first embodiment of the invention, and
FIG. 2 is a block diagram of a control system of the image forming
apparatus 100.
[0025] As shown in FIG. 1, the image forming apparatus 100 is a
tandem intermediate transfer-type full-color printer in which
yellow, magenta, cyan and black image forming portions Pa, Pb, Pc
and Pd are arrayed along an intermediate transfer belt 130.
[0026] A yellow toner image is formed on a photosensitive drum 3a
and is transferred to the transfer belt 130 in the image forming
portion Pa. In the same manner, a magenta toner image, a cyan toner
image, and a black toner image are formed on photosensitive drums
3b, 3c and 3d and are transferred to the transfer belt 130 in the
image forming portions Pb, Pc and Pd, respectively.
[0027] The four color toner images carried on the transfer belt 130
are conveyed to a secondary transfer portion T2 and are secondarily
transferred to a recording medium P collectively. The recording
medium P is pulled out of a recording medium cassette 10a by a
pickup roller, is separated one by one by a separation roller 6a
and is fed to a registration roller 12. The registration roller 12
sends the recording medium P to the secondary transfer portion T2
by adjusting timing with the toner images on the transfer belt
130.
[0028] The recording medium P on which the four color toner images
are secondarily transferred self-strips and is sent to a fixing
apparatus 9. The fixing apparatus 9 heats up and pressurizes the
recording medium P carrying the toner images to fix the toner
images on the surface of the recording medium P. Then, the
recording medium P is discharged out of the apparatus.
[0029] The image forming apparatus 100 can print successively by
repeating the operations of feed, registration, image-forming
(secondary transfer), fixation and discharge described above. The
apparatus 100 can print 80 sheets per minute for example by
transversely feeding A4-size sheets.
[0030] The image forming apparatus 100 is provided with a control
portion 141 as shown in FIG. 1. The control portion 141 manages
overall operations of the image forming apparatus 100 to form
images by controlling command systems among the respective units
while monitoring and controlling operations of the respective units
as shown in FIG. 2.
[0031] The image forming apparatus 100 is also provided with a
manipulating portion 142 as an interface for a user to access the
apparatus 100. The manipulating portion 142 allows the user to set
basic print job information such as recording medium information
such as basis weight, image information such as density, and a
number of recording media to be printed.
[0032] The image forming apparatus 100 of the present embodiment is
configured to be able to execute a so-called "consolidated job" of
printing images by consecutively switching types of recording
media. The recording medium cassettes 10a and 10b are configured to
feed plain sheets, thin sheets and thick sheets as the recording
media to a heating nip N provided in the fixing apparatus 9. The
"consolidated job" permits to print brochures for example each
composed of a thick cover sheet, documents printed on thin sheets
and pictures printed on coated sheets one by one. A user is allowed
to set details of the consolidated job such as setting of
temperature of the fixing apparatus 9 per type of the recording
medium through the manipulating portion 142.
<Image Forming Portion>
[0033] As shown in FIG. 1, the image forming portions Pa, Pb, Pc
and Pd are configured to be substantially identical except the
colors of the toners used in their respective developers 1a, 1b, 1c
and 1d. Therefore, the image forming portions Pa, Pb, Pc and Pd
will be described as the image forming portion P in general
hereinafter by excluding a, b, c and d appended at ends of the
reference numerals denoted to the respective components.
[0034] The image forming portion P is provided with a charging
roller 2, an exposure unit 5, the developer 1, a transfer roller 24
and a drum cleaner 4 disposed so as to surround a photosensitive
drum 3. The photosensitive drum 3 has an optical semiconductor
photosensitive layer formed around an outer circumferential surface
of an aluminum cylinder and rotates in a direction of an arrow
shown in FIG. 1 with predetermined processing speed.
[0035] The charging roller 2 charges the photosensitive drum 3 with
homogeneous negative dark potential VD. The exposure unit 5 scans
the photosensitive drum 3 by an ON/OFF modulated laser beam
according to scan-line image data in which a decomposed color image
of each color is developed to draw an electrostatic image on a
surface of the charged photosensitive drum 3. The developer 1
supplies toner to the photosensitive drum 3 to develop the
electrostatic image as a toner image.
[0036] The transfer roller 24 presses the transfer belt 130 to form
a transferring portion between the photosensitive drum 3 and the
transfer belt 130. The toner image carried on the photosensitive
drum 3 is transferred to the transfer belt 130 by applying DC
voltage to the transfer roller 24. The drum cleaner 4 recovers the
remaining transfer toner attached to the surface of the
photosensitive drum 3 that has passed the transferring portion by
slidingly contacting a cleaning blade to the photosensitive drum
3.
<Secondary Transfer Portion>
[0037] As shown in FIG. 1, the transfer belt 130 is wrapped around
and supported by a tension roller 15, a counter roller 14, and a
driving roller 13, and rotates in a direction of an arrow R2 by
being driven by the driving roller 13. The secondary transfer
portion T2 is configured by the transfer belt 130 supported by the
counter roller 14 and a secondary transfer roller 11 in contact
with the transfer belt 130. The toner image carried on the transfer
belt 130 is transferred secondarily to the recording medium P
conveyed to the secondary transfer portion T2 by DC voltage applied
to the secondary transfer roller 11. The belt cleaning unit 19
removes the toner and paper dust by contacting a cleaning web
(unwoven cloth) to a surface of the transfer belt 130.
[0038] The control portion 141 executes a secondary transfer roller
cleaning control operation between images (between sheets) in
consecutively forming the images and after finishing the image
forming job. The secondary transfer roller cleaning control
operation is performed to prevent degradation of the transfer
performance of the secondary transfer roller 11 and a stain of a
back side of the recording medium by recovering scattered toner and
fogging toner attached to the secondary transfer roller 11 by
applying DC voltage having the same polarity with the toner charge
for a predetermined period of time.
<Registration Rollers>
[0039] FIG. 1 shows registration rollers 12 composed of a rubber
roller made of ethylene propylene rubber with .phi.16 mm in
diameter and disposed on a back side of the recording medium and a
metallic roller made of SUS (stainless steel) with .phi.16 mm in
diameter and disposed on a front side of the recording medium to
pressurize with 1 kg of load. ASKER-C hardness of the rubber roller
is 40.degree. (1 kg load) and surface roughness Rz is about 20
.mu.m.
[0040] The registration rollers 12 prevent the recording medium
from advancing obliquely by temporarily stopping the recording
medium P by a conveying nip formed by the rubber rand metallic
rollers described above. Then, the rollers 12 feed the recording
medium P by adjusting timing for forming the image with timing for
feeding the recording medium P, such that position of an image to
be formed on the recording medium P is adequately adjusted. The
control portion 141 controls the conveyance and stoppage of the
recording medium P in feeding the recording medium P to the
secondary transfer portion T2 by rotating the rubber roller by
actuating a stepping motor not shown.
<Fixing Unit>
[0041] FIG. 3 is a diagram explaining a configuration of the fixing
apparatus in section vertical to axes of rollers described below.
As shown in FIG. 3, the recording medium P passes through the
fixing apparatus 9 from right to left in FIG. 3 and is heated and
pressed in a process of being conveyed by the heating nip N
composed of a fusing roller (image heating member) 51 disposed on
an image surface side and a pressure roller (pressurizing member)
52 disposed on a non-image surface side such that the toner image
is fixed on the surface of the recording medium P.
[0042] The fixing apparatus 9, i.e., one exemplary image heating
apparatus, controls temperature of the fusing roller 51 to a
plurality of target temperatures that correspond to types of
recording media whose basis weight and surface nature are
different. The target temperature is set such that both conveyance
(wrinkles and separability) and imaging property (fixability, toner
offset) are achieved for a non-coated sheet whose surface is paper
texture and such that the heavier the basis weight of the recording
medium, the higher the target temperature is. However, the target
temperature is set by considering glossiness of images, in addition
to the conveyance and imaging property, for a coated sheet in which
a resin layer is formed on a surface thereof. The target
temperature is set such that the heavier the basis weight, the
higher the target temperature is for a gloss coated sheet in which
a glossy coating layer is formed. However, the target temperature
is set low within a fixing permissible range for a matt coated
sheet having a coating layer whose glossiness is suppressed.
[0043] The fixing apparatus 9 forms the heating nip N by
press-contacting the fusing roller 51, whose temperature is
controlled to be more than a fusion point of the toner, and the
pressure roller 52 with each other to nip and convey the recording
medium carrying the toner image.
[0044] The fusing roller 51 is formed by wrapping an elastic layer
51b of silicon rubber with 4 mm thick around an outer circumference
of a core metal 51a, i.e., a mild steel cylindrical material,
having an outer diameter of .phi.72 mm. Then, a surface of the
elastic layer 51b is coated by a releasing layer 51c, i.e., a PFA
(tetrafluoroetylene-perfluoroalkyl vinylether copolymer) tube, of
30 .mu.m thick.
[0045] The pressure roller 52 is formed by wrapping an elastic
layer 52b of silicon rubber with 2 mm thick around an outer
circumference of a core metal 52a, i.e., a mild steel cylindrical
material, having an outer diameter of .phi.76 mm. Then, a surface
of the elastic layer 52b is coated by a releasing layer 52c, i.e.,
a PFA tube, of 30 .mu.m thick.
[0046] A lamp heater (halogen heater) 201 of 900 W, i.e., one
exemplary heater, configured to heat the image heating member is
disposed within the fusing roller 51. A temperature sensor
(thermistor) 205 is disposed in contact with the surface of the
fusing roller 51 on an exit side of the heating nip N at a center
in a rotational axial direction of the roller.
[0047] A temperature control portion 200 adjusts surface
temperature of the fusing roller 51 detected by the temperature
sensor 205 to the target temperature per each recording medium P by
controlling power supplied to the lamp heater 201 based on an
output of the temperature sensor 205.
TABLE-US-00001 TABLE 1 TARGET STANDBY TYPE OF RECORDING TEMPERATURE
OF TEMPERATURE OF MEDIUM FUSING ROLLER FUSING ROLLER THIN SHEET
160.degree. C. 180.degree. C. PLAIN SHEET 180.degree. C. FIRST
THICK SHEET 190.degree. C. SECOND THICK 200.degree. C. SHEET
[0048] As shown in Table 1, the target temperature is kept low to
prevent entangled jamming by assuring separability from the fusing
roller 51 for a thin sheet (52 to 63 g/m.sup.2), and the target
temperature is set at 160.degree. C. The target temperature for a
plain sheet (64 to 105 g/m.sup.2) is set at 180.degree. C.
[0049] Because a thermal load of the fusing roller 51 is large for
a thick sheet, the target temperature is set high in order to
assure fixability of the toner image. That is, the target
temperature of the first thick sheet (106 to 150 g/m.sup.2) is set
at 190.degree. C. and the target temperature of the second thick
sheet (150 to 220 g/m.sup.2) is set at 200.degree. C.
[0050] A standby temperature of the fusing roller 51 set during a
standby period, which enables to start to print immediately, is set
at 180.degree. C. as an initial setting such that no waiting time
is required in printing on a plain sheet frequently used. However,
the setting of the standby temperature can be changed to
190.degree. C. or 200.degree. C. through the manipulating portion
142 if the user frequently uses thick sheets.
[0051] That is, control unit 144 of the image forming apparatus 100
includes the control portion 141 and the temperature control
portion 200. The control portion 141 sets the target temperature
and the temperature control portion 200 controls the heater 201
based on the target temperature. Thus, the control unit 144 can
control the temperature of the fusing roller 51, i.e., the image
heating member, such that the temperature of the fusing roller 51
is set at the target temperature by controlling the heater (lamp
heater) 201. Still further, in heating an image formed on a
recording medium, the control portion 141 can switch the target
temperature at least from the standby target temperature which is
the target temperature during the standby state in which the fusing
roller 51 is separated from the pressure roller 52 to a first
target temperature which is the target temperature in heating an
image formed on a first recording medium such as a thick sheet for
example or to a second target temperature which is target
temperature in heating an image formed on a second recording medium
such as a thin sheet whose basis weight is smaller than that of the
first recording medium and which is lower than the standby target
temperature and the first target temperature.
[0052] It is noted that the both image heating and pressurizing
members forming the heating nip N of the fixing apparatus 9 adopt
the rollers in the present embodiment. However, at least one of the
image heating and pressurizing members may be configured by a
seamless belt. A fixing apparatus whose image heating member is
configured by the seamless belt and which is provided with a
contacting/separating mechanism to arrange the heating nip to be
releasable is also often used. Still further, although the first
recording medium is assumed to be a thick sheet in the present
embodiment, the plain sheet may be a first recording medium when a
thin sheet is adopted as the second recording medium. The thick
sheet may be also the first recording medium when the plain sheet
is the second recording medium.
<Contacting/separating Mechanism>
[0053] As shown in FIG. 3, the fixing apparatus 9 of the present
embodiment is provided with a contacting/separating mechanism 50
that allows the pressure roller 52 to pressurize and separate from
the fusing roller 51 in order to save energy and to deal with many
types of recording media. The fixing apparatus 9 stands by for the
image forming job in the state in which the pressure roller 52 is
separated from the fusing roller 51 and the temperature of the
fusing roller 51 is controlled at the target temperature of the
standby state.
[0054] It is possible to contact or separate the pressure roller 52
with/from the fusing roller 51 by actuating the
contacting/separating mechanism 50. Both end portions of the core
metal 51a of the fusing roller 51 are supported rotatably by
bearings whose level is fixed. In contrary to that, both end
portions of the core metal 52a of the pressure roller 52 are
supported by a pressurizing frame 56 turnable centering on a
turning axis 55 through an intermediary of a pressurizing spring
57, so that the pressure roller 52 can be moved up and down.
[0055] When a contacting/separating motor 207 rotates a
pressurizing cam 54 to move up a turning end of the pressurizing
frame 56, the pressure roller 52 abuts the fusing roller 51 due to
a pressurizing force of the pressurizing spring 57. In contrary,
when the contacting/separating motor 207 rotates the pressurizing
cam 54 to drop the turning end of the pressurizing frame 56, the
pressure roller 52 separates from the fusing roller 51.
[0056] The control portion 141 controls the contacting/separating
motor 207 to pressurize and release the pressure roller 52 and can
switch the state of pressurizing the fusing roller 51 with the
state separated from the fusing roller 51 within a required time of
0.8 second for example in the present embodiment. A total load of
the pressure roller 52 caused by the contacting/separating
mechanism 50 during the press-contact is about 60 kgf, so that the
heating nip N having a length of about 10 mm is formed in a sheet
conveying direction. When the pressure roller 52 is separated, a
distance from the surface of the fusing roller 51 to the surface of
the pressure roller 52 is about 2 mm in the present embodiment.
[0057] A first object of the contacting/separating mechanism 50 is
to reduce a thermal load required in heating the fusing roller 51
up to the standby temperature in activating the fixing apparatus by
separating the pressure roller 52 and thus to shorten a warm-up
time. The separation of the pressure roller 52 from the fusing
roller 51 permits to prevent the heat of the fusing roller 51 from
being deprived, to shorten the warm-up time and to considerably
reduce power consumption of the fixing apparatus 9.
[0058] A second object of the contacting/separating mechanism 50 is
to improve user's capability of handling a jammed recording medium
P by enabling to separate the pressure roller 52 when the jam
occurs.
[0059] A third object of the contacting/separating mechanism 50 is
to deal with a special recording medium by suppressing an increase
of temperature of the pressure roller 52 by reducing a time in
contact with the fusing roller 51. It is possible to reduce heat
transferred to the recording medium P passing through the heating
nip N and to suppress vapor from being generated within the tissue
of the recording medium P by preventing the increase of the
temperature of the pressure roller 52 by separating the pressure
roller 52 during when no image is formed.
[0060] However, if a wet and low basis weight coated sheet is
heated excessively, a large amount of vapor is generated within the
tissue of the recording medium P. The vapor whose move to a sheet
surface is hampered by a coated layer escapes out of a sheet back
surface, possibly making the pressure roller 52 to slip the
conveyance. There is also a possibility of causing such a
phenomenon, i.e., a so-called blister phenomenon, that the inner
vapor that cannot escape to the back surface breaks through the
surface coated layer and disturbs an image.
<Cooling Waiting Time of Fusing Roller>
[0061] When the fixing apparatus 9 that has the plurality of target
temperatures per type of the recording media switches the target
temperatures, it takes a longer waiting time in temperature control
operations in a case when the temperature is lowered than a case
when the temperature is increased. It is possible to readily
shorten a temperature increase time if a large power or IH heating
(inductive electromagnetic heating) is used. However, it is
necessary to rapidly radiate thermal energy accumulated in the
fusing roller 51 in order to lower the temperature because the
highly-productive fixing apparatus 9 adopts the fusing roller 51
whose thermal capacity is large to suppress temperature fluctuation
of the heating nip N in successively forming images. When the
recording media P are switched frequently from thick sheets to thin
sheets in the consolidated job in particular, the waiting time for
the temperature control occurs frequently and prominently, thus
influencing the total productivity of the image forming apparatus
100.
[0062] Then, in order to solve such problem, there is proposed to
dispose an air blower at an outer peripheral part of the fusing
roller 51 to lower the temperature to the target temperature by
blowing air to the fusing roller 51.
[0063] However, the air blower is required to be large to cool down
the fusing roller 51 to the desired target temperature in a short
time and the fusing roller 51 itself is enlarged to assure an air
blowing space.
[0064] Then, the fixing apparatus 9 having the
contacting/separating mechanism 50 of the present embodiment is
configured to control the temperature of the fusing roller 51 to be
an appropriate temperature uniformly and stably within a short time
by making use of roller separating and sheet conveyance sequences
corresponding to the types of the recording media P. Still further,
the fixing apparatus 9 is configured to control the temperature of
the fusing roller 51 appropriately corresponding to the types of
recording media by controlling the nip pressurizing timing in
starting to form an image.
[0065] FIG. 4 is a fixation control flowchart of the fixing
apparatus of the first embodiment, FIG. 5 is a time chart of the
fixation control implemented on a plain sheet, FIG. 6 is a time
chart of the fixation control implemented on a thin sheet, and FIG.
7 is a time chart of the fixation control implemented on a thin
sheet. Here, the unit of the basis weight g/m.sup.2 will be denoted
as gsm.
[0066] As shown in FIG. 1, the fusing roller 51, i.e., one
exemplary image heating member, heats up the image formed on the
recording medium. The pressure roller 52, i.e., one exemplary
pressurizing member, pressurizes the fusing roller 51 and forms the
nip for nipping and conveying the recording medium. The
contacting/separating mechanism 50, i.e., one exemplary
contacting/separating mechanism, contacts and separates the
pressure roller 52 with/from the fusing roller 51. The temperature
sensor 205, i.e., one exemplary temperature detecting member,
detects temperature of the fusing roller 51. The temperature
control portion 200, i.e., one exemplary power control means,
controls power of the lamp heater 201 such that the temperature of
the fusing roller 51 turns out to be a target temperature set in
advance.
[0067] With reference to FIG. 2 and as shown in FIG. 3 in
particular, the manipulating portion 142 and the control portion
141 discriminate, as one exemplary discriminating means, the types
of the recording media based on inputs of the user. The control
portion 141 discriminates the types of the recording media based on
data of a received image forming job. The control portion 141
permits to execute, as one exemplary executing portion, at least
processes of forming an image on a thick sheet, i.e., one example
of a first mode, and of forming an image on a thin sheet, i.e., one
example of a second mode.
[0068] In the process of forming the image on the thick sheet, the
temperature control portion 200 controls the power such that the
target temperature of the fusing roller 51 reaches 190.degree. C.,
i.e., one example of the first target temperature, to heat up the
image formed on the thick sheet, i.e., one example of a first
recording medium. In the process of forming the image on the thin
sheet, the temperature control portion 200 controls the power such
that the target temperature of the fusing roller 51 reaches
160.degree. C., i.e., one example of the second target temperature
which is lower than 190.degree. C., to heat up the image formed on
the thin sheet, i.e., one example of a first recording medium whose
basis weight is smaller than the basis weight of the thick
sheet.
[0069] The control portion 141 executes, as one exemplary standby
mode executing portion, processes in a standby state of the image
forming job, i.e., one exemplary standby mode. In the standby state
of the image forming job, the temperature control portion 200
controls power such that the temperature of the fusing roller 51 is
set at 180.degree. C., i.e., one example of the standby target
temperature, which is higher than 160.degree. C., i.e., the second
target temperature, in the state in which the pressure roller 52 is
separated from the fusing roller 51, to stand by for an input of an
image forming signal. When the image forming signal is input, the
control portion 141 switches the target temperature and controls
the contacting/separating mechanism 50 to start the operation for
contacting the pressure roller 52 with the fusing roller 51.
[0070] The control portion 141 controls the temperature of the
surface of the fusing roller 51 when the recording medium P enters
the heating nip N by executing the pressurizing operation of the
heating nip N of the fixing apparatus 9 by a delay time set in
advance per type of the recording medium from the sheet feeding
operation of the separation roller 6 in the first embodiment. Table
2 shows the sheet feeding ON timing and pressurizing ON timing per
type of the recording medium of the first embodiment.
TABLE-US-00002 TABLE 2 TYPE OF SHEET FEEDING PRESSURIZING HEATING
NIP RECORDING OPERATION: OPERATION: ENTERING MEDIUM ON [A] ON [B]
TIMING THIN SHEET 0 sec. 1 sec. (6 sec.) PLAIN SHEET 0 sec. 5 sec.
(6 sec.) FIRST 2 sec. 7 sec. (8 sec.) THICK SHEET SECOND 4 sec. 9
sec. (10 sec.) THICK SHEET
[0071] As shown in Table 2, the control portion 141 controls the
contacting/separating mechanism 50 and the recording medium
cassettes 10a and 10b based on the feeding timing of the recording
media set in advance per type of the recording medium and the
heating nip N forming timing. The sheet feeding ON timing and
pressurizing ON timing per type of the recording medium are set in
advance as fixed values (second) in the control portion 141. The
control portion 141 obtains the necessary sheet feeding ON timing
and the pressurizing ON timing by making reference to the types of
the recording media in Table 2. The control portion 141 operates an
internal timer when it accepts an image forming job, executes the
sheet feeding operation when the sheet feeding ON timing set in
Table 2 elapses since then, and executes the pressurizing operation
when the pressurizing ON timing elapses.
[0072] In a case of starting to heat a thin sheet from the standby
state of the image forming job, the control portion 141 prolongs a
time from when the heating nip N is formed until when the recording
medium reaches the heating nip N more than that in a case of
heating a plain sheet from the standby state of the image forming
job (C1<C2, see FIGS. 5 and 6).
[0073] In a case of starting to heat a thick sheet from the standby
state of the image forming job, the control portion 141 equalizes a
time from when the heating nip N is formed until when the recording
medium reaches the heating nip N with that of the case of heating
the plain sheet from the standby state of the image forming job
(C1=C3, see FIGS. 5 and 7).
[0074] With reference to FIG. 2 and as shown in FIG. 4 in
particular, the control portion 141 resets a JOB counter X and
starts a timer operation by receiving JOB information in Step
1.
[0075] The control portion 141 reads information related to the
type of the recording medium P contained in the JOB information and
obtains a target temperature, sheet feeding timing A (second) and
pressurizing timing B (second) of the heating nip N to be adopted
by making reference to Table 2 with the type of the recording
medium in Step 2. Then, the control portion 141 instructs the
temperature control portion 200 to switch the target temperature of
the fusing roller 51 in Step 2.
[0076] The control portion 141 judges the sheet feeding timing by
comparing the JOB counter X with the sheet feeding ON timing A in
Step 3. The control portion 141 increases the JOB counter X by unit
time of 0.1 second and repeats the judgment until when the JOB
counter X reaches the sheet feeding ON timing A (Steps 3 and 4).
Although the control portion 141 judges the sheet feeding ON timing
A per 0.1 second here, the control portion 141 may be arranged so
as to judge more finely depending on performance of the control
portion 141.
[0077] When the JOB counter X becomes equal to the sheet feeding ON
timing A (X=A), the control portion 141 actuates the registration
roller 12 to execute the sheet feeding operation in Step 5.
[0078] Then, the control portion 141 judges the pressurizing timing
by comparing the JOB counter X with the pressurizing ON timing B in
Step 6. That is, the control portion 141 increases the JOB counter
X by the unit time of 0.1 second and repeats the judgment until
when the JOB counter X reaches the pressurizing ON timing B in
Steps 6 and 7.
[0079] When the JOB counter X becomes equal to the pressurizing ON
timing B (X=B), i.e., Yes in Step 6, the control portion 141
actuates the contacting/separating motor 207 to execute the
pressurizing operation.
[0080] When the job is a consecutive image forming JOB, the control
portion 141 repeats the sheet feeding operation by the registration
roller 12 at predetermined intervals while keeping the pressurizing
state of the heating nip N until receiving JOB end information in
Steps 9 and 10. Receiving the JOB end information, i.e., Yes in
Step 9, the control portion 141 halts the sheet feeding operation
in Step 11. Then, after when the last recording medium P passes
through the fixing apparatus 9, the control portion 141 switches
the contacting/separating mechanism 50 to the separation state in
Step 11.
[0081] As shown in FIG. 5, the timing when the recording medium P
enters the heating nip N of the fixing apparatus 9 is automatically
determined from the sheet feeding ON timing. Because a conveying
distance from the separation roller 6 to the heating nip N of the
fixing apparatus 9 is 1920 mm for example and conveyance speed is
320 mm/sec. in the image forming apparatus 100 of the first
embodiment, every types of the recording media P enter the heating
nip N of the fixing apparatus 9 after 6 seconds from the sheet
feeding ON timing.
[0082] When transitions of actual surface temperatures of the
fusing and pressure rollers 51 and 52 were measured when the sheet
feeding and pressurizing operations of the first embodiment are
executed on the plain sheet, its result turned out, as follows. It
is noted that the temperature of the fusing roller 51 was measured
by the temperature sensor 205. Still further, even though the
pressure roller 52 of the fixing apparatus 9 is not provided with a
heating unit such as a lamp heater, a temperature sensor was
disposed at the same position with the fusing roller 51 and
temperature variation of the fusing roller 51 was also
measured.
[0083] Then, it was found that because the pressurizing operation
of the heating nip N is completed just before (before 0.2 second)
the recording medium P enters the fixing apparatus 9 in the case of
the plain sheet, the surface temperature of the fusing roller 51
does not drop unnecessarily and can be controlled optimally. The
control portion 141 controls the recording medium cassettes 10a and
10b such that the plain sheet arrives at the heating nip N right
after when the pressure roller 52 contacts the fusing roller 51 in
the heating process of the plain sheet.
[0084] The surface temperature of the pressure roller 52 which is
separated from the surface of the fusing roller 51 by about 2 mm in
the standby state is kept to be about 100.degree. C. by heat
radiated from the fusing roller 51. After that, in the process in
which the recording medium P is conveyed through the heating nip N,
the surface temperature of the pressure roller 52 varies within a
range of 95 to 110.degree. C. in balance with heat transferred from
the fusing roller 51 and heat radiated to the recording medium
P.
[0085] Then, it was confirmed that if the surface temperatures of
the fusing and pressure rollers 51 and 52 remain as described
above, no such slip of the roller during conveyance nor such
phenomenon that disturbs an image as described above occur at all
while assuring the image fixability even if a wet and low basis
weight coated sheet is fed. After that, the transitions of the
actual surface temperatures of the fusing and pressure rollers 51
and 52 were measured when the sheet feeding and pressurizing
operations of the first embodiment are executed in the same manner
on the thin sheet.
[0086] As shown in FIGS. 6 and 7, the control portion 141 controls
such that a time D2 from the input of the image forming signal to
the contact of the pressure rollers 52 with the fusing roller 51
when the recording medium is a thin sheet is shorter than a time D3
from the input of the image forming signal to the contact of the
pressure rollers 52 with the fusing roller 51 when the recording
medium is a thick sheet (D2<D3). The control portion 141 also
controls such that a time C2 from the contact of the pressure
roller 52 with the fusing roller 51 to the arrival of the recording
medium at the nip when the recording medium is the thin sheet is
longer than a time C3 from the contact of the pressure roller 52
with the fusing roller 51 to the arrival of the recording medium at
the nip when the recording medium is the thick sheet
(C2>C3).
[0087] In other words, the control portion 141 controls the
contacting/separating mechanism 50 such that the time D from when
the image forming signal is input until when the pressure roller
(pressurizing member) 52 in the standby state contacts the fusing
roller (image heating member) 51 and forms the nip is shorter in a
case when the target temperature of the fusing roller 51 is the
second target temperature i.e., the target temperature of the thin
sheet, than in a case when the target temperature of the fusing
roller 51 is the first target temperature i.e., the target
temperature of the thick sheet (D2<D3). The control portion 141
also controls the recording medium feeding timing such that the
time C from when the pressure roller 52 contacts the fusing roller
51 and forms the nip until when the recording medium arrives at the
nip is longer in the case when the target temperature of the fusing
roller 51 is the second target temperature than in the case when
the target temperature is the first target temperature
(C2>C3).
[0088] Still further, when the recording medium is the thin sheet,
the control portion 141 controls such that the time D2 from the
input of the image forming signal to the contact of the pressure
roller 52 with the fusing roller 51 is shorter than the time C2
from the contact of the pressure roller 52 with the fusing roller
51 to the arrival of the recording medium to the nip (D2<C2).
That is, when the target temperature of the fusing roller 51 is the
second target temperature, the control portion 141 controls the
recording medium feeding timing and the contacting/separating
mechanism 50 such that the time D2 from when the image forming
signal is input until when the pressure roller 52 in the standby
state contact the fusing roller 51 and forms the nip is shorter
than the time C2 from when the pressure roller 52 in the standby
state contact the fusing roller 51 and forms the nip until when the
recording medium arrives at the nip (D2<C2).
[0089] Still further, the control portion 141 controls such that
the time D3 from the input of the image forming signal to the
contact of the pressure roller 52 with the fusing roller 51 when
the recording medium is the thick sheet is longer than the time C3
from the contact of the pressure roller 52 with the fusing roller
51 to the arrival of the recording medium at the nip (D3>C3).
That is, when the target temperature of the fusing roller 51 is the
first target temperature, the control portion 141 controls the
recording medium feeding timing and the contacting/separating
mechanism 50 such that the time D3 from when the image forming
signal is input until when the pressure rollers 52 in the standby
state contacts with the fusing roller 51 and forms the nip is
longer than the time C3 from when the pressure rollers 52 contacts
with the fusing roller 51 and forms the nip until when the
recording medium arrives at the nip (D3>C3).
[0090] As shown in Table 2, as compared to the plain sheet, the
pressurizing ON timing of the thin sheet is quick even though the
their sheet feeding ON timings are the same. In the heating process
of the thin sheet, the control portion 141 contacts the pressure
roller 52 with the fusing roller 51 in the same time as the
temperature control portion 200 switches the target temperature in
the standby state to the second target temperature.
[0091] As a result, extra heat of the fusing roller 51 is
transferred to the pressure roller 52 and the drop of the surface
temperature of the fusing roller 51 is accelerated until when the
recording medium P arrives at the heating nip N, so that the
temperature of the fusing roller 51 reaches the target temperature
of 160.degree. C. quickly more than a comparative example 1. The
comparative example 1 indicates transition of the surface
temperature of the fusing roller 51 when the target temperature is
lowered from 180.degree. C. to 160.degree. C. on starting a job and
when no recording medium P is fed without contacting the pressure
roller 52 with the fusing roller 51. Because the surface
temperature of the fusing roller 51 does not drop due to the
contact of the pressure roller 52 in the comparative example 1, a
downtime close to 20 seconds is required until when the surface
temperature of the fusing roller 51 drops to 160.degree. C.
[0092] The comparative example 2 indicates transition of the
surface temperature of the fusing roller 51 only when the
pressurizing operation is executed without executing the sheet
feeding operation in the control of the first embodiment. In the
comparative example 2, because the recording medium P is not
conveyed to the heating nip N at the time when the surface
temperature of the fusing roller 51 drops to 160.degree. C., the
removal of heat of the fusing roller 51 by the pressure roller 52
still continues, dropping the surface temperature of the fusing
roller 51 below 160.degree. C. Even though the temperature control
portion 200 actuates the lamp heater 201 after that to control the
surface temperature of the fusing roller 51 so as to be 160.degree.
C., a downtime close to 20 seconds is required in any way when the
recording medium is fed and a feeding time of 6 seconds is added
after that.
[0093] As compared to the comparative example 2 that cools the
fusing roller 51 by simply contacting the pressure roller 52 with
the fusing roller 51, the control of the first embodiment shortens
a waiting time (downtime) in forming an image after switching the
target temperatures. It is possible to suppress temperature
variation of the heating nip N during when the recording medium is
conveyed by lessening the drop of temperature of the fusing roller
51 by timely inserting the thin sheet whose effect of removing the
heat of the fusing roller 51 is smaller than that of the pressure
roller 52 through the heating nip N.
[0094] According to the control of the first embodiment, the
recording medium is sent to and is heated in the heating nip N in a
transient state of dropping the temperature of the image heating
member from the target temperature of the standby state to the
second target temperature. Therefore, a time for waiting for the
start of formation of an image is considerably shortened as
compared to a case of starting to form an image by waiting for the
time when the temperature of the image heating member ends to drop
and is stabilized at the second target temperature.
[0095] According to the control of the first embodiment, it is
possible to downsize the apparatus because the temperature of the
image heating member is controlled by using existing
contacting/separating mechanism. Still further, even if image
forming apparatus is configured to use a cool fan, in addition to
the control of the present embodiment, it is possible to downsize
the cooling fan and the apparatus.
[0096] According to the control of the first embodiment, unevenness
of distribution of temperature of the fusing roller 51 hardly
occurs in the direction of the rotational axis as compared to the
case of cooling by the cooling fan. Then, it is possible to control
the fusing roller 51 at the optimal temperature stably without
requiring a new waiting time when the recording medium is the thin
sheet.
[0097] According to the control of the first embodiment, it is
possible to execute the optimal sheet feeding operation sequence
and the pressurizing operation sequence per type of the recording
medium. Thereby, it is possible to control the surface temperature
of the fusing roller 51 at the appropriate target temperature
corresponding to a selected recording medium P stably without
unevenness by the minimum waiting time as the image forming
apparatus 100.
[0098] FIG. 7 shows the transition of the actual surface
temperatures of the fusing and pressure rollers 51 and 52 when the
sheet feeding and pressurizing operations of the first embodiment
are executed in the same manner also on the thick sheet. As shown
in Table 2, the pressurizing ON timing of the thick sheet is set
just before when the recording medium P arrives at the heating nip
N similarly to the case of the plain sheet in order to reduce the
drop of the temperature of the fusing roller 51 caused by the
contact with the pressure roller 52. In the heating process of a
thick sheet, the control portion 141 controls the recording medium
cassettes 10a and 10b such that the plain sheet arrives at the
heating nip N right after when the pressure roller 52 contacts with
the fusing roller 51.
[0099] However, the temperature of the fusing roller 51 cannot
reach the desired temperature before an arrival of the sheet to the
nip if the sheet feeding operation is started with the same timing
with that of the plain sheet, so that the sheet feeding ON timing
is delayed by 2 seconds more than that of the plain sheet to assure
a time for increasing the temperature of the fusing roller 51.
Although the delay time of 2 seconds can be shortened by increasing
power of the lamp heater 201, the fixing apparatus 9 is arranged to
be able to control the temperature of the fusing roller 51 by a
minimum waiting time that satisfies the fixability in the present
embodiment.
[0100] It is noted that the examples of the control of the control
portion 141 when the target temperature of the standby state is
180.degree. C. and the second target temperature is 160.degree. C.
have been explained in the first embodiment. However, in a case
when a type of recording medium whose second target temperature is
still lower and a difference of temperature with the target
temperature of the standby state is large, the drop of the
temperature of the fusing roller 51 is accelerated by prolonging
the time from when the heating nip N is formed till when the
recording medium arrives at the heating nip N.
[0101] Still further, in the heating process of the thin sheet, the
control portion 141 controls the recording medium feeding step such
that the thin sheet arrives at the heating nip N before when the
temperature of the fusing roller 51 drops from 180.degree. C. to
160.degree. C..degree. C. and such that the temperature of the
fusing roller 51 reaches to the second target temperature in the
process when the thin sheet passes through the heating nip N.
[0102] This arrangement enables the fusing roller 51 to heat the
sheet within a range close to the second target temperature by
preventing an overshoot of the drop of the temperature of the
heating nip N by utilizing thermal insulating property of the
recording medium.
[0103] It is noted that the target temperature during the standby
state of the image forming job is not limited to be 180.degree. C.,
i.e., the target temperature of the plain sheet, and it is possible
to select arbitrary temperature lower than 200.degree. C., i.e.,
the target temperature of the thick sheet 2. Still further, the
standby target temperature may be any temperature as long as the
temperature is less than the first target temperature, and when a
first recording medium is a plain sheet and a second recording
medium is a thin sheet, this standby target temperature is
equalized with the first target temperature.
Second Embodiment
[0104] FIG. 8 is a fixing control flowchart of a second embodiment.
The sheet feeding and pressurizing operations of the second
embodiment are executed in the same timing with that of the first
embodiment after starting the image forming job. Therefore, the
operations of the image forming apparatus 100, the transmission of
the temperatures of the fusing and pressure rollers 51 and 52 shown
in FIGS. 5, 6 and 7 and effects of the second embodiment are the
same with those of the first embodiment. However, while the sheet
feeding operation is controlled by the separation roller in the
first embodiment, the control of the sheet feeding operation is
executed by the registration roller 12 in the second embodiment.
Accordingly, only a difference from the first embodiment will be
explained in the following explanation and the configurations in
common with those of the first embodiment will be omitted here.
[0105] Table 3 shows registration operation ON (sheet feeding)
timing and the pressurizing operation ON timing per each type of
the recording medium in the second embodiment.
TABLE-US-00003 TABLE 3 TYPE OF REGISTRATION PRESSURIZING HEATING
NIP RECORDING OPERATION: OPERATION: ENTERING MEDIUM ON [A] ON [B]
TIMING THIN SHEET 3 sec. 1 sec. (6 sec.) PLAIN SHEET 3 sec. 5 sec.
(6 sec.) FIRST 5 sec. 7 sec. (8 sec.) THICK SHEET SECOND 7 sec. 9
sec. (10 sec.) THICK SHEET
[0106] The sheet feeding ON timings of the separating roller 6 in
Table 2 are replaced with registration operation ON timings
respectively shifted by 3 seconds from the sheet feeding ON timings
in Table 3. The registration operation ON timing is timing when the
recording medium P is started to be sent out by the registration
roller 12.
[0107] As shown in FIG. 1, when the image forming job is started,
the registration roller 12 temporarily stops the recording medium P
regardless of the type of the recording medium after when the
separating roller 6 starts the sheet feeding operation. Then, the
registration roller 12 is started to be driven again at the
registration operation ON timing obtained by making reference to
the type of the recording medium in Table 3, the toner image is
transferred to the recording medium P and the fixing apparatus 9 is
conveyed to the fixing apparatus 9.
[0108] By making reference to FIG. 2 and as shown in FIG. 8 in
particular, the control portion 141 executes the judgment flow
which is basically the same with that of the first embodiment shown
in FIG. 4. However, differing from the first embodiment, an order
which precedes among the registration operation and the
pressurizing operation differs depending on the type of the
recording medium P. When the recording medium is the thin sheet for
example, the registration operation ON timing A=3 seconds and the
pressurizing ON timing B=1 second, so that the pressurizing
operation of the heating nip N precedes the registration operation.
When the recording medium is the plain sheet, the registration
operation ON timing A=3 seconds and the pressurizing ON timing B=5
seconds, so that the registration operation of the registration
roller 12 precedes the pressurizing operation. Therefore, the
respective operations are judged every time when the judgment is
made in the flow of the second embodiment. Then, after judging that
the both operations are completed, the control shifts to the
judgment of end of JOB in Step 9.
[0109] According to the control of the second embodiment, it is
possible to execute the recording medium P conveying operation more
accurately because the registration roller 12 is closer to the
fixing apparatus 9 more than the separating roller 6. Therefore, it
is possible to stably control the surface temperature of the fusing
roller 51, when the recording medium P arrives at the heating nip
N, to be close to the target temperature.
Third Embodiment
[0110] FIG. 9 is a fixing control flowchart of a third embodiment,
FIG. 10 is a time chart of the fixing control implemented on the
thin sheet, and FIG. 11 is a time chart illustrating effects of the
control of the third embodiment. In the third embodiment, the
control portion 141 judges the registration operation ON timing in
the second embodiment not by making reference to the fixed time
table by the JOB counter but by current temperature of the fusing
roller 51 detected by the temperature sensor 205. Therefore, only
the difference from the second embodiment will be explained in the
following description and an explanation of the configurations in
common with those of the second embodiment will be omitted
here.
[0111] As shown in FIG. 2, the control portion 141 starts to convey
the recording medium when the temperature sensor 205 reaches to
predetermined temperature in the process of drop of the temperature
of the fusing roller 51 from the standby state target temperature
of 180.degree. C. to the second target temperature of 160.degree.
C., and sends out of the registration roller 12. Table 4 shows the
registration operation ON (sheet feeding) timing and the
pressurizing ON timing per type of the recording medium in the
third embodiment.
TABLE-US-00004 TABLE 4 TYPE OF RECORDING REGISTRATION PRESSURIZING
HEATING NIP ENTERING MEDIUM OPERATION: ON [A] OPERATION: ON [B]
TIMING THIN SHEET CURRENT TEMPERATURE < 165.degree. C. 1 sec.
(REGISTRATION OPERATION: ON + 3 sec.) PLAIN SHEET CURRENT
TEMPERATURE < 175.degree. C. (REGISTRATION (REGISTRATION
OPERATION: OPERATION: ON + 2 sec.) ON + 3 sec.) FIRST THICK SHEET
CURRENT TEMPERATURE < 185.degree. C. (REGISTRATION (REGISTRATION
OPERATION: OPERATION: ON + 2 sec.) ON + 3 sec.) SECOND THICK SHEET
CURRENT TEMPERATURE < 195.degree. C. (REGISTRATION (REGISTRATION
OPERATION: OPERATION: ON + 2 sec.) ON + 3 sec.)
[0112] As shown in Table 4, when the recording medium is the thin
sheet, the control portion 141 executes the pressurizing operation
of the pressure roller 52 in the same time with the switch of the
target temperature of the fusing roller 51 from 180.degree. C. to
160.degree. C. after one second from receiving an image forming
job. Thereby, the control portion 141 executes the registration
operation of the registration roller 12 (delivery of the recording
medium P) when the detected result of the temperature sensor 205
drops from 180.degree. C. to 165.degree. C. or less.
[0113] When the recording medium is the plain sheet, the control
portion 141 executes the delivery of the recording medium P by the
registration roller 12 when the detected result of the temperature
sensor 205 is 175.degree. C. or more, the control portion 141
executes the registration operation immediately in the standby
state at 180.degree. C. and executes the pressurizing operation of
the pressure roller 52 after two seconds from the registration
operation. With this arrangement, the recording medium P arrives at
the heating nip N right after when the heating nip N is formed. The
two seconds is a time required for the recording medium P delivered
by the registration roller 12 to be conveyed to the heating nip
N.
[0114] When the recording medium is the first thick sheet, the
control portion 141 switches the target temperature of the fusing
roller 51 from 180.degree. C. to 190.degree. C. after one second
after receiving the image forming job. After that, the control
portion 141 executes the delivery of the recording medium P by the
registration roller 12 when the detected result of the temperature
sensor 205 rises from 180.degree. C. and exceeds 185.degree. C. In
the case of the second thick sheet, the control portion 141
increases the temperature of the fusing roller 51 to 200.degree. C.
and executes the delivery of the recording medium P by the
registration roller 12 when the detected result of the temperature
sensor 205 exceeds 195.degree. C.
[0115] With reference to FIG. 2 and as shown in FIG. 9 in
particular, the control portion 141 resets the JOB counter X and
starts the timer operation after receiving JOB information in Step
1.
[0116] The control portion 141 reads information on the type of the
recording medium P contained in the JOB information and obtains
target temperature to be used, executing temperature A (.degree.
C.) of the registration operation, and the pressurizing time B
(second) of the heating nip N by making reference to the types of
the recording media in Table 4 in Step 2. Then, the control portion
141 switches the target temperature of the fusing roller 51 by
commanding to the temperature control portion 200 in Step 2.
[0117] As shown in Table 4, when the recording medium is the plain
sheet, the first thick sheet or the second thick sheet, the
pressurizing timing B (second) is represented not by a fixed value
(second) but by a relative value (second) to the registration
operation timing, so that an initial value of the value B is set
provisionally at 100 seconds. Then, when the registration operation
is executed after judging the temperature of the temperature sensor
205 in Step 5, the value B is set again by adding two seconds to
the registration operation timing.
[0118] The control portion 141 judges the sheet feeding timing by
comparing level of the current temperature of the fusing roller 51
detected by the temperature sensor 205 with that of the temperature
A of the registration operation ON in Table 4 in Step 3. Then, the
control portion 141 repeats the judgment in Steps 3, 6 and 12 by
increasing the JOB counter X by 0.1 second in Step 7 until reaching
to the temperature A of the registration operation ON, i.e., No in
Step 3.
[0119] When the current temperature of the fusing roller 51 is
equalized with the temperature A, i.e., Yes in Step 3, the control
portion 141 actuates the registration roller 12 and executes the
sheet feeding operation in Step 5. The pressurizing timing B
(second) of the heating nip N is set by adding two seconds to the
time at that moment.
[0120] The control portion 141 judges the pressurizing timing by
comparing the JOB counter X with the pressurizing ON timing in Step
6. The control portion 141 repeats the judgment (Steps 6 and 12) by
increasing the JOB counter X by 0.1 second of unit time until
reaching to the pressurizing ON timing B, i.e., No in Step 6. Then,
when JOB counter X=B, i.e., Yes in Step 6, the control portion 141
actuates the contacting/separating motor 207 to execute the
pressurizing operation in Step 8.
[0121] When the registration operation and the pressurizing
operation end, i.e., Yes in Step 12, the control portion 141 judges
whether or not the JOB ends in Step 9. The control portion 141
repeats the sheet feeding operation of the registration roller 12
at predetermined intervals until when it receives information of
the end of JOB in Step 10. When the control portion 141 receives
the information on the end of JOB, i.e., Yes in Step 9, the control
portion 141 halts the sheet feeding operation of the registration
roller 12 and switches the contacting/separating mechanism 50 to
the separated condition after when the last recording medium P
passes through the fixing apparatus 9 in Step 11.
[0122] The registration operation is executed in a stage when the
temperature of the fusing roller 51 converges to a certain
temperature per each recording medium in the control of the third
embodiment, so that the temperature of the fusing roller 51 varies
less when the same type of recording medium passes through the
heating nip N as compared to the first embodiment in which the
registration operation is executed with the fixed seconds.
[0123] As a result, it is possible to absorb variation of
temperature of the core metal 51a of the fusing roller 51
accumulated by hysteresis of the image forming jobs and variation
of a temperature drop curve of the fusing roller 51 caused by
outside temperature and others of the image forming apparatus 100
for example. Therefore, it is possible to control the temperature
of the fusing roller 51 stably more than the first embodiment.
[0124] FIGS. 10 and 11 show the effects of the control of the third
embodiment confirmed by experiments that the variation of the
temperature of the fusing roller 51 is small when the same type of
recording medium passes through the heating nip N. That is, FIG. 10
shows transitions of the temperatures of the fusing and pressure
rollers 51 and 52 in a first image forming job on the thin sheet
after activating the image forming apparatus 100. FIG. 11 shows
transitions of the temperatures of the fusing roller 51 and the
pressure roller 52 when the image forming job is executed on the
same thin sheet with that of FIG. 10 right after repeating five
times of consecutive image forming JOBs on 100 plain sheets.
[0125] As shown in FIG. 10, differing from the first and second
embodiments, the registration operation is executed by making
reference to the actual transition of the temperature of the fusing
roller 51 in the third embodiment, so that it is possible to
control the temperature accurately corresponding to the
environment.
[0126] As shown in FIG. 11, because the temperature of the core
metal 51a of the fusing roller 51 is high when the consecutive
image forming jobs of plain sheets are executed immediately before
the execution of the image forming job of the thin sheet, the drop
of the temperature of the fusing roller 51 is delayed even if the
pressurizing operation is executed with the same timing with FIG.
10. That is, the arrival to 165.degree. C. where the registration
operation is ON is delayed by about one second as compared to FIG.
10.
[0127] However, it is possible to constantly reproduce the
temperature of the fusing roller 51 when the recording medium P
actually passes through the heating nip N by judging the
registration operation timing not by the fixed elapsed time from
the start of the JOB but by the detected result of the temperature
sensor 205. With this arrangement, it is possible to eliminate
differences of glossiness of fixed images or of fixing qualities.
The optimal sequence that is not affected by the ambient
environment of the image forming apparatus 100 or the just previous
state of use enables to control the temperature of the fusing
roller 51 more stably than the first and second embodiments. It is
thus possible to control the surface temperature of the fusing
roller 51 stably in a shortest possible waiting time in the state
of use of the image forming apparatus by implementing the optimal
recording medium feeding operations and the pressurizing operation
of the heating nip corresponding to the type of the recording
medium.
Fourth Embodiment
[0128] FIG. 12 is a fixing control flowchart of a fourth
embodiment. The fourth embodiment is the same with the third
embodiment except that the temperature for judging the registration
operation ON is replaced with temperature and humidity within the
image forming apparatus 100. Therefore, steps in FIG. 12 in common
with those in the third embodiment will be denoted by the same
reference numerals in FIG. 9 and an overlapped explanation thereof
will be omitted here. FIG. 12 is different from FIG. 9 only in a
part of Step 2. An explanation of the other configurations in
common with those of the third embodiment will be also omitted
here.
[0129] As shown in FIG. 1, the temperature and humidity sensor 208,
i.e., one exemplary humidity sensor, detects humidity within the
image forming apparatus 100. The control portion 141 sets the
temperature such that the higher the absolute humidity, the lower
the temperature is in starting to convey the recording medium in
the fourth embodiment. The temperature and humidity sensor 208 is
attached at a location close to the recording medium cassette 10
within the image forming apparatus 100 to detect humidity and
moisture of the recording medium P on which an image is formed.
That is, the temperature and humidity sensor 208 detects the
temperature and humidity of a storing portion of the recording
medium on which an image is formed.
[0130] The control portion 141 changes the temperature for judging
the registration operation ON by temperature information detected
by the temperature and humidity sensor 208 and by absolute humidity
(humidity g contained in 1 kg of air) calculated from the
temperature information and relative humidity information. The
control portion 141 controls such that the higher the absolute
humidity based on an output of the temperature and humidity sensor
208, the lower the predetermined temperature for sending out the
recording medium is. Table 5 shows the sheet feeding ON timing and
pressurizing ON timing per type of the recording medium in the
fourth embodiment.
TABLE-US-00005 TABLE 5 TYPE OF RECORDING PRESSURIZING HEATING NIP
ENTERING MEDIUM REGISTRATION OPERATION: ON [A] OPERATION: ON [B]
TIMING THIN SHEET MOISTURE, 10 g/kg OR MORE: CURRENT 1 sec.
(REGISTRATION OPERATION: ON + TEMPERATURE < 165.degree. C. 3
sec.) MOISTURE LESS, THAN 10 g/kg: CURRENT TEMPERATURE <
170.degree. C. PLAIN SHEET OUTSIDE TEMPERATURE, LESS THAN
15.degree. C.: (REGISTRATION OPERATION: (REGISTRATION OPERATION: ON
+ CURRENT TEMPERATURE < 175.degree. C. ON + 2 sec.) 3 sec.)
OUTSIDE TEMPERATURE, 15.degree. C. OR MORE: CURRENT TEMPERATURE
< 170.degree. C. FIRST THICK OUTSIDE TEMPERATURE, LESS THAN
15.degree. C.: (REGISTRATION OPERATION: (REGISTRATION OPERATION: ON
+ SHEET CURRENT TEMPERATURE < 185.degree. C. ON + 2 sec.) 3
sec.) OUTSIDE TEMPERATURE, 15.degree. C. OR MORE: CURRENT
TEMPERATURE < 180.degree. C. SECOND THICK OUTSIDE TEMPERATURE,
LESS THAN 15.degree. C.: (REGISTRATION OPERATION: (REGISTRATION
OPERATION: ON + SHEET CURRENT TEMPERATURE < 195.degree. C. ON +
2 sec.) 3 sec.) OUTSIDE TEMPERATURE, 15.degree. C. OR MORE: CURRENT
TEMPERATURE < 190.degree. C.
[0131] As shown in Table 5, the temperature [A] for judging the
registration operation ON of Table 4 is selected in two stages from
the detected result of the temperature and humidity sensor 208. The
selection is made to shorten a recording medium feeding waiting
time in the consolidated job. In other words, the switching of JOB
is implemented in a necessary shortest possible waiting time to
improve the productivity of the consolidated job.
[0132] A range of the temperature of the fusing roller 51 that
satisfies the fixability in the case of the thick sheet 2 is
different depending on temperature of the recording medium P in the
recording medium cassette 10. The temperature for judging the
registration operation in the case of the thick sheet 2 is bounded
by environmental temperature of 15.degree. C. Because the
fixability is worsened when the temperature of the recording medium
P is lower than 15.degree. C., the control portion 141 starts to
feed the sheet after fully increasing the temperature of the fusing
roller 51 to 195.degree. C. or more in switching to the thick sheet
2 in the consolidated job of the thick sheet 2 and the thin
sheet.
[0133] A range of the temperature of the fusing roller 51 that
satisfies the separability of the thin sheet differs depending on
the moisture of the recording medium P in the recording medium
cassette 10. The temperature for judging the registration operation
in the case of the thin sheet is bounded by 10 g/kg (correspond to
27 cc/70% RH) of humidity. The separability from the fusing roller
51 is worsened if the moisture of the recording medium P is 10 g/kg
or more, so that the control portion 141 starts to feed the sheet
after fully lowering the temperature of the fusing roller 51 in
switching to the thin sheet in the consolidated job of the thick
sheet 2 and the thin sheet.
[0134] A secondary object of the fourth embodiment is to improve a
life of the fixing apparatus 9. Shortening of the recording medium
feeding waiting time leads to shortening of an operation time of
the fixing apparatus 9 per number of formed images and then to
shortening of driving time of the fusing roller 51, the pressure
roller 52 and the related sliding members. Thus, the improvement of
the productivity of the consolidated job leads to the improvement
of the durability and the life of the fixing apparatus 9 by
reducing frequency of replacing parts of the fixing apparatus
9.
[0135] By making reference to FIG. 2 and as shown in FIG. 12 in
particular, the control portion 141 obtains the temperature
[A].degree. C. for judging the registration operation selectively
from Table 5 based on the output information of the temperature and
humidity sensor 208 in Step 3.
[0136] When the consolidated job of the thin sheet and the thick
sheet 2 is executed by changing the environment by the image
forming apparatus 100 carrying the fixing control system of the
fourth embodiment, an effect of shortening the feed waiting time of
20 seconds in maximum is obtained in switching the types of the
recording media as a result. The consolidated job can be executed
without damaging the separability of the thin sheet and the
fixability of the thick sheet 2 and without causing any problems in
the basic function such as output image quality. Thus, the
compativility of the improvement of the productivity and the basic
function of the consolidated job can be demonstrated by optimizing
the control of the temperature of the fusing roller 51
corresponding to the environmental conditions. It is also possible
to improve the productivity of the consolidated job and the
durability and the life of the fusing roller 51 while keeping the
basic functions by changing the sequence corresponding to the
environment detected information. It is noted the larger the number
of prints of the image forming job, the greater the effect of
shortening a time taking to finish the image forming job is, and
the shortening effect varies depending on the type of the recording
medium P and on the experimental and environmental conditions.
Fifth Embodiment
[0137] The roller-type fixing apparatus in which the both image
heating member and pressurizing member are rollers has been
explained in the first through fourth embodiments. In contrary to
that, a belt-type fixing apparatus in which a fixing nip is formed
by an endless belt and a roller disposed inside of the belt as
either or both of the image heating member and pressurizing member
in a fifth embodiment.
[0138] While the tandem-type intermediate transferring color
printer in which the image forming portions are arrayed along the
intermediate transfer belt has been illustrated in the first
through fourth embodiment, the image forming apparatus is not
limited to that. That is, the image forming apparatus may be a one
drum-type intermediate transferring color printer in which the
respective color toner images are formed sequentially on one image
carrier and are transferred to an intermediate transfer member or a
tandem-type direct transferring color printer which has no
intermediate transfer member and in which the respective color
toner images are transferred directly from an image carrier to a
recording medium. Still further, the image forming apparatus may be
other image forming apparatuses such as a copier and facsimile
other than a printer.
[0139] No lamp heater is provided for the pressure roller 52 and
the surface temperature of the pressure roller 52 is not also
controlled in the first through fourth embodiments described above.
However, it is possible to provide a lamp heater or the like for
the pressure roller 52 and to control the surface temperature of
the pressure roller 52 at constant temperature lower than that of
the fusing roller 51 by about 50.degree. C. That is, the
temperature of the pressure roller 52 as the pressurizing member at
least needs to be lower than the temperature of the fusing roller
51 when the pressure roller 52 contacts the fusing roller 51 as the
image heating member from the standby state and forms the nip in
the embodiments described above. To that end, even if a heater for
heating the pressurizing member is provided, the standby target
temperature of the pressurizing member is set to be lower than the
standby target temperature of the image heating member as well.
[0140] The fixing apparatus of the embodiments described above may
be carried out by other modes in which part or whole of the
configuration of the embodiments are replaced with their
substitutional configuration as long as the temperature of the
image heating member is controlled by adjusting the timing for
contacting the pressurizing member with the image heating
member.
[0141] Accordingly, the image heating member and the pressurizing
member may be belt members or roller members as long as the image
forming apparatus is configured to be able to contact/separate the
image heating member with/from the pressurizing member. The heating
system of the image heating member (system of the heater) is not
limited to be the lamp heater, and may be any heating system such
as an inductive heating, resistive heating, radiation heating and
heat pipe system. The invention can be carried out in any type of
image forming apparatus such as a charging type, exposure type,
developing type, tandem type or one drum type, intermediate
transfer type, recording medium conveying type or sheet conveying
type image forming apparatuses. Although the only main parts
related to the formation and transfer of the toner images have been
explained in the embodiments described above, the invention may be
carried out in various uses such printers, various printing
machines, copiers, facsimile machines and multifunction printers.
Still further, the contacting/separating mechanism needs not be the
mechanism using the cam as described above, and may be any
mechanism such as one that directly moves up and down the pressure
roller by using a linear actuator. Furthermore, although the
control unit 144 includes the control portion 141 and the
temperature control portion 200 in the embodiments described above,
the control unit may be composed of one control portion or of a
polarity of control portions.
[0142] While the embodiments of the invention have been explained
above, the invention is not limited to the embodiments described
above. Still further, the effects described in the embodiments of
the invention are merely the most suitable effects brought about by
the invention and the effects of the invention are not limited by
those described in the embodiments of the invention.
[0143] Aspects of the present invention can also be realized by a
computer (such as a CPU or MPU) of a system or apparatus that reads
out and executes a program recorded on a memory device to perform
the functions of the above-described embodiment(s), and by a
method, the steps of which are performed by a computer of a system
or apparatus by, for example, reading out and executing a program
recorded on a memory device to perform the functions of the
above-described embodiment(s). For this purpose, the program is
provided to the computer for example via a network or from a
recording medium of various types serving as the memory device,
e.g., computer-readable medium. In an example, a computer-readable
storage medium may store a program that causes a sheet storage
apparatus to perform a method described herein. In another example,
a central processing unit (CPU) may be configured to control at
least one unit utilized in a method or apparatus described
herein.
[0144] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0145] This application claims the benefit of Japanese Patent
Application No. 2011-264057, filed Dec. 1, 2011, which is hereby
incorporated by reference herein in its entirety.
* * * * *